What type of nut has two radial lines 120° apart?

The correct answer is associated with the identification of the specific type of nut based on markings and standards used in the fasteners industry. A nut that features two radial lines spaced 120 degrees apart is designated as a Grade 5 nut. This particular marking helps distinguish the strength and properties of the nut, indicating a medium strength level compared to other grades. Grade 5 nuts are often utilized in applications where moderate strength is sufficient, making them a popular choice in automotive and machinery contexts. The radial lines are part of the standardized identification system that allows manufacturers and users to easily recognize and select the appropriate nuts for specific fastening needs.